You know, your question reminds me of a couple other science questions from curious readers. Evangeline, age 7, wants to know why her hair is black. Sureya, age 8, wants to know why some people have curly hair.

It just so happens that one of my favorite science projects explores our questions about what makes us unique. It has to do with our DNA, or the blueprint for life.

My claws can come in quite handy when I need to scratch my ears or climb trees. I bet you’ve found that your own fingernails can be useful tools, too. Perhaps you’ve used them to pick up a penny or peel an orange.